Campag4life

I just built up a Roubaix Pro for distance riding in '12 and wonder about the one bolt seatpost that came with the frameset. Below is a pic from the PDF that describes the torque spec for the bolt...which looks to be a pure compression joint.
Initially I apparently didn't torque it enough...spec is a full 10 ft-lbs which is a lot for a little allen wrench....as when riding the saddle on the trainer, the saddle tilted rearward. I then found the torque spec and used a torque wrench and was surprised how much I under torqued the joint...what I though was 120 in-lbs was about 70% of that. So much for my calibrated hand. Its a clever seat post design without question and Specialized is known for their good engineering...but...I haven't had the best experience with one bolt clamps of any ilk in the past and have always preferred a 2 bolt seat post clamp like a Thomson clamp design. Will this post maintain the seat tilt I set initially?...will it stay in place for a 185# rider?...or have others discarded it for a more reliable 2 bolt design? Setback is OK...looks to be about 20mm or so. No doubt there are lots of Specialized riders on this forum that ride this seat post or at least used to.
Please weigh in with your findings if you would. I wonder whether I should order a 2 bolt carbon post to replace it...one I don't have to worry about the tilt adjustment changing as I ride?
Thanks

hodie21

Everyone I have ever owned I had to crank it down pretty hard. One bolt design is nice but you feel like you are going to break the seatpost tightening it down.

Commodus

The design looks identical to the post on my gf's Giant. My experience was the same as yours, I didn't torque it nearly enough. Once I did, it has been in place for more than a year. Of course she weighs a lot less than you, but I weigh as much as 160 and it has been stable under me as well.

I'm not sure how relevant that is to your post because of the different manufacturers, but I do believe that the traditional cause of failure of a one bolt post is the bolt shearing. I see this a lot of cross races. This design doesn't appear to place that kind of force on the bolt, but rather shares the load between the fancy 'nut' and the shoulders on the 'cup surfaces'.

Bobsled

I had one at one point and sold it for a Thomson. Mostly because of the slight setback the Specialized SP had but also for looks of the Thomson. I never had a problem w/ the seat tilting once I torqued it to the recommended torque.

Campag4life

Thanks guys. Bob...I too have ridden Thomson posts in the past but if anything this post has more offset than any Thomson...Thomson offset post is only 16mm. Don't know the spec on this post but it appears to have about 25mm of setback...measures 25mm from bolt center to post centerline..a fair amount of offset.
As to looks, I like the looks of the Specialized post so no issue there. Also, word about the Roubaix carbon seat post is...it is a very compliant post and Thomson's tend to be quite rigid...which some may prefer.
What I will probably do is start with 10 ft-lbs and see if it stays in place. Then I will go to 11..then 12...
Please weigh in with your experience if you have one of these...believe this seat post joint is used on the Tarmac and perhaps even Venge...tho not certain about the Venge.

caloso

Agree with the others that it's a pretty neat design but it's easy to under-torque. (Which is bad news if you hit the right bump on a ride far from home and didn't remember to bring along a tool. Ask me how I know this.) If you don't have a torque wrench, crank it down pretty good, ride it around the block, make sure it's still level, then crank it down even more.

Campag4life

Seems to be the case...thanks. The thing is...10 ft-lbs with a small L shaped allen carried in one's jersey pocket...is some serious reffing down. That's what threw me off when I mounted the seat up for the first time...a Toupe. Not used to applying that kind of torque with a little hand held allen wrench.
My 3/8" drive torque wrench is about a foot long...and that means applying 10 lbs to the handle end. How 'bout that math? By contrast it takes about 40 lbs of hand pressure on a 3 inch long allen...quite a bit.

Possible the new Tarmac is a two bolt design...maybe somebody can confirm. I have seen the same two bolt post on a couple of new Tarmacs. Here is a pic of a 2012 Tarmac SL4 Pro. Also included a pic of the incredible Venge. Now note that the Venge which uses a proprietary post shape...is the same one bolt compression joint. Honestly that is not a good deal as far as I am concerned. Thing I like about round posts is...you have the option of installing the post you prefer.

svtmike

Mine hasn't ever moved except when I wanted it to (I've had the bike for two seasons), but I've always torqued it to spec.

jmX

Neat design except that it doesn't work with any of Specialized's Pro Saddles.

I ditched mine for a Thomson, which was also much lighter.

Campag4life

SVTmike...how much do you weigh?...if you don't mind me asking.

jmX...are you speaking of Specialized carbon rail saddles? Would see odd if you couldn't put a Specialized carbon railed saddle on a Venge.

Looigi

Trek is pretty much the same thing. When I picked up my wife's Madone the dealer reinforced the necessity to torque the seat screw as specified. I'm not a big fan of the design as it's a bit of a pain to assemble and get the seat angle set just right. Greasing the cones is essential.

svtmike

Around 190 most of the year.

And jmX is right -- the carbon rail saddles are not compatible because the one bolt design compresses the rails from the sides rather than top to bottom.

Soil_Sampler

+1

Campag4life

Stands to reason that Specialized isn't going to put a seat post out there on the majority of their high end bikes that isn't going to work well...but then again Campy made that crappy one bolt seat post for years....maybe still does

Appreciate the validation that if torqued to spec the tilt mechanism should hold even with my 185# load on it.
Thanks guys.

grwoolf

I've used the old 1-bolt with no issue and my new Tarmac has a 2-bolt design that you can use with carbon rails. I think I prefer the 2-bolt design, but they are both fine.